Syria is majority Sunni Muslim, with substantial Alawite, Christian, Druze, Ismaili, and Twelver Shia communities and a Yazidi presence in the northeast. It holds one of the oldest continuous Christian populations in the world, and Damascus has been a major centre of both Islam and Christianity for centuries. Reliable percentages do not exist: the last full census predates 2011 and displacement has changed the distribution.
Syria is a majority Muslim country that has never been religiously uniform, and the mix is part of what makes it worth understanding. Precise percentages are unreliable: the last full census predates the war, and thirteen years of displacement have moved millions of people both internally and abroad.
The majority are Sunni Muslims, spread across every region. Alongside them are Alawites, concentrated in the coastal mountains; Christians of many churches, including Greek Orthodox, Syriac Orthodox, Armenian, Melkite, and Maronite; Druze, mainly in Jabal al-Arab in the south; Ismailis around Salamiyah; Twelver Shia; and a Yazidi presence in the northeast.
For a visitor, the practical consequence is that you will see churches and mosques on the same street in Damascus and Aleppo, and that the calendar carries both sets of holidays. The Religion pillar covers each community in proper depth.